DESCRIPTION (adapted from abstract) Health consequences resulting from exposure to xenoestrogens and antiestrogens are expected. Because of the potential human health effects, regulatory agencies are now considering the requirement for industrial chemical with potential environmental and human exposure to be evaluated for their estrogenicity. The US Safe Drinking Water Act was passed on June 25, 1997 which included screening of drinking waters for chemicals that mimic estrogen. There is a commercial need for contract service to test industrial and environmental chemicals for estrogen modulating potential. The objective of this proposal is to develop a unique, novel and relevant in vitro assay which can be used for the screening of industrial chemicals and environmental samples for estrogen modulation activity. The assay employs an estrogen responsive human breast cancer cell line, MCF-7 cells. Preliminary studies have shown that estrogen exposure results in development of multicellular nodules or foci in confluent cultures of MCF-7 cells. The development of these foci appears to be estrogen specific and is suppressed by antiestrogens. The specific aim of the Phase I research program is the development of optimized conditions for estrogen dependent focus development. A standard protocol will be developed in which conditions are optimized through systematic evaluation of all relevant technical factors. These will include selection of tissue culture supplies and conditions, serum requirement and concentration, assay format and evaluation, timing and cell proliferation parameters, and generation and selection of highly sensitive and stable MCF-7 clones. PROPOSED COMMERCIAL APPLICATIONS: Potential commercial application not available.